This application is a continuation-in-part of U.S. Ser. No. 170,839 filed 3/21/88, now abandoned.
This invention relates to a regiospecific carbonylation process for making acyl compounds from aromatic heterocyclic compounds, and, more particularly, to a catalyzed carbonylation process for the regiospecific preparation of ortho-substituted acyl compounds by reacting an aromatic sulfur or nitrogen heterocycle in the presence of an olefin.
Functionalized aromatic compounds, including aromatic heterocyclic compounds, are key intermediates in many areas of industrial organic chemistry and have substantial uses of their own in a variety of fields. Many of such materials are typically prepared by gas-phase alkylation of such substances as benzene, toluene or xylene using sieve catalysts or in the liquid phase by the more conventional Friedel-Crafts alkylation technology. Whereas many alkyl-substituted aromatics are readily prepared in the gas phase using molecular sieve catalysts, heterocyclic compounds are either difficult to functionalize using this method or the reactions are not regiospecific. Although regiospecific methods exist for alkylating or acylating this type of compound, existing techniques involve expensive materials such as lithium metal and/or are difficult to carry out on a large scale. Other less difficult and/or expensive methods of preparation such as radicalbased processes are not regiospecific and give mixtures of isomers. See, for example, U.S. Pat. Nos. 4,376,860; 4,098,908; 3,979,400; and 3,840,507.
Several papers reporting on the interaction of N-heterocyclics with Ru.sub.3 (CO).sub.12 have been published recently. In J. Organometallic Chem. 314, 311-22 (1986), pyridine, 2,2'-bipyridyl, pyrazole, 3,5-dimethylpyrazole and its perfluorinated derivative have been shown to react with triruthenium dodecacarbonyl to form isolatable solids. In the case of pyridine and 2,2'-bipyridyl, the compounds react to displace carbon monoxide and form a N-Ru bond. A C-Ru bond is formed also by inserting one of the cluster Ru atoms into a C--H bond ortho to the heterocyclic atom. Described in Organometallics 5, 2193-8 (1986) is the reaction with triruthenium dodecacarbonyl of quinoline, 1,2,3,4-tetrahydroquinoline, phenanthradine and 9,10-dihydrophenanthradine where similar complexes are obtained.
Now it has been found that one class of acyl compounds, ortho-substituted ketones of aromatic, nitrogen-containing heterocyclics, can be formed cheaply and highly regioselectively by catalytically carbonylating a combination of an aromatic nitrogen heterocycle and an olefin in the presence of a ruthenium carbonyl compound. This reaction appears quite general and only requires that the aromatic, nitrogen-containing heterocycle contain an unsubstituted carbon atom ortho to the ring nitrogen atom. Such compounds as 2-pyridyl ethyl ketone can be formed with close to 100% selectivity to the o-substituted isomer, which materials have substantial uses in the pharmaceutical, agricultural, and plating fields and as inhibitors for plastics.